1 Field of the Invention
The present invention relates to a process and an apparatus for manufacturing tyres for vehicle wheels, in particular for manufacturing tyres different from each other.
The present invention further relates to an apparatus for manufacturing at least one reinforcement structure on a tyre component formed on a forming support, such apparatus being usable for manufacturing tyres for vehicle wheels, in particular tyres different from each other.
2 Description of the Related Art
A tyre for vehicle wheels generally comprises a carcass structure comprising at least one carcass ply formed of reinforcing cords embedded in an elastomeric matrix. The carcass ply has end edges respectively engaged with annular anchoring structures. The latter are arranged in the areas of the tyre usually identified by the name “beads” and each of them is normally formed by a substantially circumferential annular insert on which at least one filling insert is applied, in a radially outer position thereof. Such annular inserts are commonly identified as “bead cores” and have the task of keeping the tyre firmly fixed to the anchoring seat specifically provided in the rim of the wheel, thus preventing, in operation, the radially inner end edge of the tyre coming out from such a seat.
At the beads specific reinforcing structures may be provided having the function of improving the torque transmission to the tyre.
In a radially outer position with respect to the carcass ply a belt structure comprising one or more belt layers is associated, said belt layers being arranged radially one on top of the other and having textile or metallic reinforcing cords with crossed orientation and/or an orientation substantially parallel to the direction of circumferential extension of the tyre.
Between the carcass structure and the belt structure a layer of elastomeric material, known as “under-belt”, can be provided, said layer having the function of making the radially outer surface of the carcass structure as uniform as possible for the subsequent application of the belt structure.
In a radially outer position with respect to the belt structure a tread band is applied, also made of elastomeric material.
Between the tread band and the belt structure a so-called “under-layer” of elastomeric material can be arranged, said under-layer having properties suitable for ensuring a steady union of the tread band itself.
On the side surfaces of the carcass structure respective sidewalls of elastomeric material are also applied, each extending from one of the side edges of the tread band up to the respective annular anchoring structure to the beads.
The traditional processes for manufacturing tyres for vehicle wheels essentially provide for the components of the tyre listed above to be first made separately from one another, to be then assembled on at least one building drum.
However, the current tendency is that of using manufacturing processes that allow the manufacturing and storage of semi-finished parts to be minimised or possibly eliminated.
Attention has now turned towards process solutions that allow the individual components of the tyre to be made by directly building them, according to a predetermined sequence, onto a forming support, typically toroidal or cylindrical.
The term “reinforced continuous band-like element” is used to indicate a continuous element comprising one or more thread-like reinforcing elements, such as textile or metal cords, substantially parallel to one another and embedded in a matrix of elastomeric material or coated with a layer of elastomeric material.
Preferably, such reinforcing cords extend parallel to each other along the direction of longitudinal extension of the same reinforced continuous band-like element.
A cutting to size of said reinforced continuous band-like element, fed along a feeding direction, generates a “reinforcing element”.
“Cutting length” is defined as the measure of said reinforcement element along said feeding direction of the reinforced continuous band-like element.
The term: “elastomeric material” is used to indicate a composition comprising at least one elastomeric polymer and at least one reinforcing filler. Preferably, such a composition further comprises additives such as, for example, a cross-linking agent and/or a plasticizer. Thanks to the provision of the cross-linking agent, such material may be cross linked by heating, so as to make the end product.
The terms “radial” and “axial” and the expressions “radially inner/outer” and “axially inner/outer” are used with reference to the radial direction and to the axial direction of a forming support used for building a specific tyre component. The terms “circumferential” and “circumferentially” instead, are used referring to the annular extension of the forming support.
The expression “tyre component” is used to indicate any structural element of a tyre, or even just a portion of such structural element, which is suitable for carrying out a specific function when the tyre is used in a running vehicle. Such component may be for example the liner, the under-liner, the abrasion-proof element, the bead core, the bead filler, the carcass ply, the belt strip, the under-belt layer, the under-layer of the tread band, the sidewall inserts, the sidewalls, the tread band, the reinforcement inserts, etc.
The expression “barycentric grip condition” and/or “barycentric position” is used to indicate a condition and/or position wherein the reinforcement element is gripped or held at a surface portion thereof extending symmetrically on opposite sides with respect to the barycentre of the reinforcement element.
EP 0 956 940 describes a process for manufacturing a reinforcement layer in a tyre being formed on a forming support. Such reinforcement layer is obtained by sequentially depositing a plurality of reinforcement elements on the forming support, along a circumferential direction of an outer peripheral surface thereof. Such reinforcement elements are cut to size in a proper cutting group from a reinforcement band-like element. Subsequent to the cut, each reinforcement element is picked up by proper gripping members and deposited on the outer peripheral surface of the forming support.
WO 2010/067139 describes a process for manufacturing tyres for vehicle wheels, wherein a reinforcement annular structure is associated at each one of the axially opposite end edges of a carcass ply deposited on a substantially cylindrical forming support, such annular reinforcement structure being obtained by deposition on the carcass ply of a plurality of reinforcement elements cut to size from a reinforced continuous band-like element fed in the proximity of the forming support. Each reinforcement element, once cut to size, is picked up by a gripping member for the subsequent deposition on the carcass ply. In particular, in a preferred embodiment, the gripping member transfers the reinforcement element to a positioning member which in turn deposits it on the respective end edge of the carcass ply.